Browse Prior Art Database

Key Card Programs Motherboard to Accept Wide Variety of PowerPC PGA Processors

IP.com Disclosure Number: IPCOM000123200D
Original Publication Date: 1998-Jul-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 33K

Publishing Venue

IBM

Related People

Hoang, B: AUTHOR [+3]

Abstract

It was desired to design a motherboard which would accept a wide variety of speeds and types of PowerPC processors into a zero insertion force PGA socket. This would allow one design to be used in several different products and would allow customer upgrade. However, there are a number of functions which must be set at power-on before the processor can fetch any code whatsoever. These include the bus clock speed, the core operating frequency ratio, and certain modes like the bus width and no-data-retry. Furthermore, PPC processors are not equipped with identification pins.

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This is the abbreviated version, containing approximately 92% of the total text.

Key Card Programs Motherboard to Accept Wide Variety of PowerPC PGA
Processors

   It was desired to design a motherboard which would accept a
wide variety of speeds and types of PowerPC processors into a zero
insertion force PGA socket.  This would allow one design to be used
in several different products and would allow customer upgrade.
However, there are a number of functions which must be set at
power-on before the processor can fetch any code whatsoever.  These
include the bus clock speed, the core operating frequency ratio, and
certain modes like the bus width and no-data-retry.  Furthermore, PPC
processors are not equipped with identification pins.

   The prior solution was to incorporate a number of jumpers
which could be factory set to personalize the board to the processor
to be installed.  Approximately 15 such jumpers are required.  This
would not be acceptable for customer use.

   The solution was to route all jumper wires to a small
edge connector and to design a "key card" to insert into the
connector.  The key card contains only etch and has no components.
There is one key card for each processor type supported.  Each card
is designed to ground or float the appropriate jumper wires in order
to set the correct power-on state for that processor.  To upgrade,
one inserts the new processor and the corresponding key card.  The
cost is kept low by selecting a low-cost connector and by eliminating
all
active or passive components from the key card.  ...